1. Field of the Invention
The present invention relates to an economical method for replacing bearing pads from bridge hinges and bridge abutments, and retrofitting seismic resistant structures with load-bearing pipes, with the aid of small hydraulic jacks.
2. Description of the Related Art
The related art shows various jacking techniques for construction of various structures. The art of interest will be discussed in the order of their perceived relevance to the present invention.
French Patent Application No. 2,576,948 published on Aug. 8, 1986, for Michel Guichard et al. describes a joint forming method for buildings by using hydraulic jacks in cylindrical cavities to hold the joint open while the filling sets. A row of cylindrical apertures of two different diameters are made along the line of the joint which are to be fitted together have hydraulic jacks with a pair of curved thrust plates inserted into each larger aperture. The jacks separate the joint for insertion of a sealant which is allowed to solidify before the jacks are removed. At first glance, one might conclude the processes are similar because hydraulic jacks and curved thrust plates are similar to the apparatus utilized in the present invention. However, the present invention is not utilizing the hydraulic jack in a horizontal position which would require strenuous effort to place the heavy hydraulic jack and the accompanying curved thrust plates in an upward direction into the cavity with the longitudinal axis of the jack held in a horizontal position by individual adjustment of each jack to stay in position. The present inventive method does not require an extended period for maintaining the separation of a joint as in the joint sealing method of the reference. There are no suggestions for (1) utilizing the jack in a different position for removal and insertion of a bearing pad or a pipe and (2) unifying the thrusts of the jacks in the separation process.
Japanese Patent No. 280,110 issued on Nov. 10, 1989, to Shinichi Yamazaki describes two methods for lifting a bridge girder from an abutment with a jack to permit the placement of a packing material. In the first method of FIGS. 1a-1d, a hanger is attached to the underside of a girder by a bolt in a lug of the hanger in a free space made available by a first saddle on a step. There is no suggestion for forming the existing access space by other means. As best understood, the hanger has a rotating bolt attached to the head of the jack. A second saddle is placed on top of the first saddle, the jack and the feed bench is retracted and rotated to permit the addition of a packing material under the jack. In the second embodiment of FIGS. 3a-3g, there is no hanger and a packing material is already under the jack. The jack is extended to add a second saddle on the step. The jack is removed and placed on a second packing material and extended presumably to add another saddle on the step. This reference is distinguished by the lack of forming an entry and in numerous repetitions of stroking the jack.
French Patent No. 2,544,432 issued Oct. 19, 1984, to Michel Placidi et al. describes a heavy duty hydraulic jack used to separate an aqueduct portion from an abutment by placing the jack horizontally with its head bolted onto the aqueduct portion lo increase the distance between the aqueduct portion and the abutment. There is no suggestion for forming an entry for replacement of elastomeric bearing pads as in the present invention.
European Patent Office Patent Application No. 423,029 published on Apr. 17, 1991, for Daniel Demarthe describes an obliquely positioned large ram installation for sliding a bridge section from land to piles. This huge jack and the process of using same are distinguished by its extreme size and different use.
U.S. Pat. No. 3,564,567 issued on Feb. 16, 1971, to Viliman Mladyenovitch describes a building method for multi-span structures utilizing timber towers topped with hydraulic jacks and ending with the end portions of the bridge.
U.S. Pat. No. 5,566,414 issued on Oct. 22, 1996, to Haluo (sic) Nonaka describes a bridge raising and supporting method and a device consisting of a wedge-shaped drive member cooperating with an upper wedge-shaped pressure receiving member attached to a sliding rod of a horizontally mounted hydraulic jack. A plate shaped shoe is inserted between the upper wedge member and the bridge structure. After wedging up the bridge structure, the jack portion is removed to leave in the wedges. There is no suggestion for forming holes to replace bearing pads in the bridge structure.
U.S. Pat. No. 3,685,224 issued on Aug. 22, 1972, to Pierre Launay describes a method of advancing a prestressed concrete bridging structure, i.e., a deck section, over piers by arranging two hydraulic jacks resting on neoprene plates on the shoulders of a concrete pier. Slide shoes which abut the deck section are made of reinforced elastomer with a bottom layer of tetrafluoroethylene and slide over a formation of three concrete slabs, wherein the center slab has a covering of a plate of stainless steel. The function of the jacks in this method appear to ensure that the slide shoes are not crushed and, therefore, have no relevance to the present invention.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a jacking for bridge hinges solving the aforementioned problems is desired.